Field of the Invention
This invention relates to a change-over valve assembly for switching a direction of a fluid flow, and more particularly to a poppet-seal type change-over valve assembly which is capable of switching a direction of a fluid flow in a simple and secure manner.
Existing change-over valves are largely classified into two types, that is, spool type valves and poppet type valves. A spool valve has its spool; advantages that (a) it requires a reduced number of component parts and therefore simple in construction; (b) it allows multi-directional and multi-positional change-over operations simply by altering various dimensions of a single spool; and (c) it can easily be adapted into a pressure-balanced construction which permits appreciable reductions in the required valve operating force and can cope with a relatively large fluid flow especially when a direct actuation type electromagnetic valve operating system is used. However, the spool valve has inherent drawbacks that (a) it is difficult to establish a secure fluid seal on the sliding portions of the spool, (b) the fluid drains and dusts or foreign matter in the fluid are apt to creep into the sliding portions and contribute to increase the frictional resistance of the spool to an abnormally high level as will cause operational failures of the valve and as will lead to a burning loss of a solenoid where a direct actuation type electromagnetic valve operating system is employed, unless the quality of the fluid is controlled with utmost care.
On the other hand, a poppet valve has advantages that (a) it can seal the fluid in a secure manner; (b) a large fluid flow is obtained by a small displacement of the valve; and (c) it is free from operational failures due to fluid drains and dusts and does not require prohibitively strict quality control of the fluid. However, with the existing poppet valves, difficulties are encountered in that (a) it is difficult to fabricate the valve in a pressure-balanced construction which requires only a minimized operating force; and (b) in order to effect the change-over operation in more than three directions or at more than three positions, it is necessary to employ a corresponding number of valve units, resulting in a valve assembly which has an increased number of component parts and which is disadvantageously large in size and high in production cost.
The spool valves and poppet valves are contrastive to each other in operational characteristics as mentioned hereinabove and are therefore used for different purposes in practical applications. It is the general practice to employ a spool valve for a change-over operation in more than three directions and to employ a poppet valve for a change-over operation in less than three or in two directions. There exists a four-directional or four-ways poppet type change-over valve which is constituted by a number of two- or three-way valve units or by a shaft carrying a number of poppet valve seats in a manner similar to spool valves. However, the former is disadvantageous in that it requires an increased number of component parts and complicated construction for providing passages interconnecting the respective valve units, resulting in a valve assembly of an unduly large size and high production cost. The latter may be provided in a small size like the spool valves but has a drawback that it is difficult to distribute an axially acting valve operating force uniformly to a number of poppet seal portions as components of the operating force.
It is therefore an object of the present invention to provide a poppet type change-over valve assembly which has a simple construction comparable to spool valves and which requires only a small amount of operating force for establishing a secure and tight valve seal.
It is another object of the present invention to provide a poppet type change-over valve assembly which can deal with even a contaminated fluid without inviting operational failures of the valve.
It is still another object of the present invention to provide a poppet type change-over valve which can operate either as a single-operation type change-over valve or double-operation type change-over valve as the case may be with slight dimensional modifications.
In one preferred form of the invention, the poppet type change-over valve assembly comprises a valve casing interiorly defining a generally cylindrical valve chamber and having valve guiding cavities at opposite ends thereof and a pair of opposingly disposed conical valve seats; a main valve body slidably received in said valve chamber and having sliding end portions in hermetical engagement with walls of said valve guiding cavities of said valve casing and a pair of opposingly disposed conical valve seats provided between said sliding end portions in face to face relation with said conical valve seats of said valve casing; an annular float valve loosely mounted around said main valve body and having parallel outer and inner sealing edges for engagement with said conical valve seats of said valve casing and said main valve body;
said conical valve seats of said main valve body and valve casing and said float valve being in a dimensional relationship dictated by an inequality .psi..degree. &lt; 180.degree. - .theta..degree. &lt; .theta..degree. where .psi..degree. is a cone angle defining the conical valve seats of said main valve body, .phi..degree. is a cone angle defining the conical valve seats of said valve casing, and .theta..degree. is a cone angle containing two diagonally disposed sealing edges of said float valve; PA1 said conical valve seats of said main valve body and valve casing and said float valve being in a dimensional relationship as defined hereinbefore; PA1 said conical valve seats of said main valve body and valve casing and said float valve being in a dimensional relationship as defined hereinbefore;
a valve biasing means for urging said main valve body to assume a first change-over position; and a valve operating means provided at one end of said valve casing for shifting said main valve body into a second change-over position against action of said valve biasing means; said float valve being tightly held between said conical valve seats of said main valve body and said valve casing by the action of said main valve body and a fluid pressure prevailing in said valve chamber when said main valve body is shifted to either said first or second change-over position, thereby establishing a tight seal around said main valve body for connecting a fluid inlet port with a selected fluid output port.
In another preferred form of the invention, the poppet type change-over valve assembly comprises; a valve casing interiorly defining a generally cylindrical valve chamber and having valve guiding cavities at opposite ends thereof and a pair of opposingly disposed conical valve seats; a main valve body slidably received in said valve chamber and having sliding end portions in hermetical engagement with said valve guiding cavities of said valve chamber and a pair of opposingly disposed conical valve seats provided between said sliding end portions in face to face relation with said conical valve seats of said valve casing; an annular float valve loosely mounted around said main valve body and having parallel outer and inner sealing edges for engagement with said conical valve seats of said valve casing and said main valve body;
a valve biasing means for urging said main valve body to assume a first change-over position; a valve operating means provided at one end of said valve casing for shifting said main valve body into a second change-over position against action of said valve biasing means; and a fluid exhaust passage extending axially through said main valve body and opening into said valve chamber through a radial port between said paired conical valve seats of said main valve body; said float valve being tightly held between said conical valve seats of said main valve body and said valve casing by the action of said main valve body and a fluid pressure prevailing in said valve chamber when said main valve body is shifted either said first or second change-over position, thereby establishing a seal around said main valve body for connecting a fluid inlet port with a selected fluid output port while communicating a switched-off fluid output port with an exhaust port through said fluid exhaust passage in said main valve body.
In still another preferred form of the invention, the poppet type change-over valve assembly comprises; a valve casing interiorly defining a generally cylindrical valve chamber and having valve guiding cavities at opposite ends thereof and a pair of opposingly disposed conical valve seats; a main valve body slidably received in said valve chamber and having sliding end portions in hermetical engagement with walls of said valve guiding cavities of said valve casing and a pair of opposingly disposed conical valve seats provided between said sliding end portions in face to face relation with said conical valve seats of said valve casing; an annular float valve loosely mounted around said main valve body and having parallel outer and inner sealing edges for engagement with said conical valve seats of said valve casing and said main valve body;
a valve biasing means for urging said main valve body to assume a first change-over position; a float valve guiding means for maintaining said float valve in coaxial alignment with said main valve body; and a valve operating means provided at one end of said valve casing for shifting said main valve body into a second change-over position against the action of said valve biasing means; a fluid exhaust passage extending axially through said main valve body and opening into said valve chamber through a radial port provided between said paired conical valve seats on said main valve body; said float valve being tightly held between said conical valve seats of said main valve body and said valve casing by cooperation of said main valve body and a fluid pressure prevailing in said valve chamber when said main valve body is shifted to either said first or second change-over position, thereby establishing a tight seal around said main valve body for connecting a fluid inlet port with a selected fluid output port while communicating a switched-off fluid output port with an exhaust port through said fluid exhaust passage in said main valve body.
One of the features of the present invention residues in that a float valve is mounted floatingly in a space between the valve casing and the main valve body. In the first and second change-over positions, a valve seal established by the float valve, the conical valve seats on the casing and the main valve body is maintained securely by a combined action of a force applied by a suitable valve operating mechanism and a supplied fluid pressure acting on the float valve per se. The main valve body may be shifted from the first change-over position to the second change-over position or vice versa by means of an extremely small operating force regardless of the magnitude of the fluid pressure acting on the float valve.
Moreover, since the float valve is mounted loosely with respect to the main valve body in such a manner that the fluid pressure acting on the float valve would not give any influence on the operation of the main valve body, the valve can be imparted with a pressure-balanced construction as in balanced spool type change-over valves or can operate as a single-action type change-over valve which returns to an initial position under the influence of a fluid pressure or as a self-retaining double-action type change-over which is continuedly retained in a switched position under the influence of the fluid pressure. The valve assembly of the invention can thus serve for various purposes owing to its high versatility in function.
Furthermore, the change-over valve according to the present invention has the advantages of both the existing spool type valves and the poppet type valves without inheriting their inherent drawbacks as mentioned hereinabove.